A model for bubble motion in non-uniform electric fields

Electrohydrodynamic effects on bubble motion in dielectric fluids has found positive application for enhanced boiling heat transfer, for example in refrigerators. However the motion of bubbles in columns of dielectric fluid is also of interest where the presence of bubbles may adversely affect the breakdown performance of the liquid dielectric when employed as an electrical insulation. This is the case for superconducting power apparatus designs where liquid nitrogen is used as both coolant and electrical insulation. A model is presented for the bubble motion in a dielectric fluid under the influence of dielectrophoretic force. A model has been developed by analysis of the forces acting upon a bubble within a non-uniform electric field with rod-plane electrode geometry. This set of differential equations can be solved numerically to determine the bubble trajectory for a specified applied voltage. Model results are compared to experimental data for a range of voltages obtained in a column of liquid nitrogen.